Radio-contrast enhancement of a urinary tract calculus

We report the case of a woman who presented with obstruction and urosepsis of her left kidney secondary to small cystine calculi, The calculi could no t be seen on initial plain abdominal X-ray. However, following percutaneous nephrostogram the calculi became more radio-dense and visible on later X-r ays. Experimental enhancement of calculi has been described before but not in man. We presume that the contrast medium was adsorbed by the calculus to increase the radio-density. Further investigation of this phenomenon could prove useful in the management of complex radiolucent calculi.